This disclosure relates to lead-acid batteries and, more particularly, to a method and apparatus for delivering molten lead or a lead alloy to the cast-on-strap molds used in the manufacture and assembly of lead-acid batteries.
Electrochemical storage batteries, and in particular, lead sulfuric acid storage batteries are ubiquitous in automotive applications. These batteries have electrochemical cells developing about 2.1 Volts each. Generally, six of these cells are connected in series to produce the 12 Volt battery known as a SLI (starting, lighting, ignition) battery common in automobile systems.
The cell elements comprise a series of alternating positive and negative plates with separators positioned therebetween. The electrical connections for the positive plates, and the negative plates as well, are typically made by a strap which connects the lugs of individual plates together. The straps are made of a wide variety of molten lead, or, more usually, lead-based alloys.
Various machines have been developed and used over the years to cast the straps onto the cell elements in a semi-continuous manner. Such machines have often been termed xe2x80x9ccast-on-strap machinesxe2x80x9d. Generally, cast-on-strap (COS) machines require inserting the cell element upside down into a mold for the strap. The lug elements for the respective plates are thus positioned in a mold containing the requisite molten lead or molten lead alloy, and the molten material is allowed to solidify. The cell element is then removed with the cast-on-strap in place.
Typically in COS machines, stacked battery plates and separators for a plurality of cells making up a lead-acid storage battery have the respective connection lugs on the positive and negative plates of each cell interconnected by a cast-on strap and an intercell connecting post or terminal post cast as an integral portion of each strap. These casting operations are accomplished simultaneously with the cells inverted but otherwise oriented as they are to be in the finished battery structure. Stacked cell elements are clamped with the plate lugs extending downward. A plurality of properly oriented mold cavities (e.g., 12 cavities for a 12V battery) are preheated then molten lead is poured or flows into each mold cavity. The clamped cell assemblies are positioned to immerse a portion of the plate connecting lug on each plate in the molten mass in an appropriate connector strap cavity. The cavities are then chilled, as by flowing water through the body of the mold, and when the molded straps and posts solidify adequately they are extracted from the mold with the plates fused thereto.
Mold expense is a significant factor in machines of the type under consideration. It has been difficult to obtain suitable castings in which mold forms can be produced. The variety of cell and terminal arrangements required for lead-acid batteries has further complicated mold construction. Furthermore, the simultaneous casting operation discussed above necessitates large expensive molds and large casting machines.
In accordance with the above, it is desirable to improve mold assemblies for battery strap and post cast-on machines. It is further desired to decrease cycle time of battery strap and post cast-on machines while reducing the cost and size of mold assemblies and casting machines.
A method and apparatus for preparing connecting straps and end terminals for lead batteries by filling selected cavities of one or two molds is disclosed. A first mold includes five mold cavities in an upper face thereof, whereby at least two preselected cavities of the five mold cavities are translationally aligned to be filled with lead to form a first strap/post terminal configuration while another at least two preselected cavities of the first mold form a second strap/terminal configuration. A second mold includes five mold cavities in an upper face thereof that form third and fourth strap/post terminal configurations depending on which two cavities are selected and translationally aligned to be filled with lead. The first and seconds molds form four different strap/post configurations for connecting individual cells formed from the two molds in a multi-cell battery. In another embodiment, a single mold includes five cavities in an upper face thereof, whereby at least two preselected cavities of the five mold cavities are selected to form a selected strap/terminal configuration. The single mold forms four different strap/post configurations for connecting individual cells formed from the two molds in a multi-cell battery.
In another embodiment, a method for casting straps onto storage battery plates is disclosed. The method includes providing a source of molten lead, receiving a first mold block having five mold cavities in an upper face thereof in a first molding station, whereby at least two preselected cavities of the five mold cavities are filled with lead, translating the mold block to align each of the at least two preselected cavities with the source of molten lead, and translating the battery plate group or the mold block toward a battery plate group to dip lugs of the group into the at least two preselected cavities and allow solidification of the molten lead producing a molded cell for placement in a multi-cell battery.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following brief description of the drawings.